1/4 cup toasted sesame seeds
One or 2 hours before cooking, rinse the mung bean sprouts so that they have time to drain thoroughly.
Cut the chicken into thin strips. Add the marinade ingredients, adding the cornstarch last. Marinate the chicken for 20 to 25 min.
To prepare the sauce, in a small bowl dissolve the 1 tbs cornstarch with the 4 tbs water. Whisk the water or chicken broth with the oyster sauce, soy sauce, salt, pepper and cornstarch and water mixture and set aside.
Soften the noodles by placing them in boiling salted water. Plunge into cold water to stop the cooking process and drain thoroughly.
Wash all the vegetables as needed. Cut the celery and the bok choy into 1/2-inch pieces on the diagonal. If substituting broccoli for bok choy, peel the stalks until no more strings come out, and slice thinly on the diagonal. Wipe the mushrooms clean with a damp cloth and slice. Cut the red bell pepper in half, remove the seeds and cut into chunks. Peel and chop the onion. Dice the green onion.
Heat a wok or frying pan over medium-high to high heat. Add 2 tbs oil. When the oil is hot, add the noodles. Fry in batches until golden. Remove the noodles from the pan.
Heat 2 tbs oil. Add the onion and the meat. Let the meat brown briefly, then stir-fry until the redness is gone and the meat is nearly cooked through. Remove the cooked meat and onion from the pan.
Cook the rest of the vegetables separately, except for the green onion, seasoning each with a bit of salt while stir-frying if desired. When cooking the bok choy or broccoli, add 1/4 cup of water and cover while cooking. Remove each of the vegetables from the pan when finished stir-frying. Add more oil as needed.
Give the sauce a quick re-stir. Add all the ingredients back into the wok, making a "well" in the middle of the wok for the sauce. Add the sauce, stirring quickly to thicken. Mix everything together. Stir in the green onions. Pour the cooked vegetable and sauce mixture on top of the noodles. Garnish the chow mein with the toasted sesame seeds. Serve hot. Serves 4-6